Field of the Invention
The present disclosure relates to a method and apparatus for converting chemical energy stored in wastewater into electrical energy, and particularly to a zero chamber, no interface system electrically interconnecting a biofilm to a power harvester.
Description of Related Art
The use of microbial fuel cells (MFCs) to generate electricity from organic substances provides numerous benefits including operation at ambient temperatures and pressures. Moreover, because the oxidation reactions which occur in a MFC typically do not require aeration, MFCs generally have reduced power requirements. The lack of aeration may hamper the breakdown of organic compounds (Cheng H et al. 2015 Water Research 81(72-83) in traditional chambered MFCs).
Traditional two-chamber MFCs typically use an anode chamber and a separate cathode chamber. In general, these chambers are separated by a proton exchange membrane (PEM) and are electrically connected through an external circuit. In the anode chamber, bacteria generate electrons and gain energy for growth by oxidizing available nutrients. Electricity is then typically produced by transferring the generated electrons to the anode. Protons created as a result of the oxidation migrate through the proton exchange membrane and combine with the electrons in the presence of oxygen at the cathode to form water in the cathode chamber. In such MFCs, the electrodes may include various forms of conductive material, for example carbon paper or carbon cloth, such as those manufactured by the E-TEK Division of BASF Fuel Cell, Inc. while materials such as a sulfonated tetrafluorethylene copolymer (e.g., Nafion) may be used as exchange membranes in two-chamber MFCs. Electrodes may be further enhanced with catalysts, such as platinum (Pt), to improve their performance.
A single-chamber MFC includes an open ended chamber having both an anode and a cathode, but lacks an exchange membrane. The two electrodes are typically fixed at opposite ends of the chamber, with the anode embedded at the base of the chamber, and a two-sided cathode forming an interphase with a water-tight seal on an end of the chamber, wherein the chamber is filled with biodegradable nutrients and bacteria.
While the single-chamber MFC offers benefits over the two chamber MFC, the single-chamber MFC still requires two electrodes, typically of specialty materials. The single chamber MFC also creates the interphase, wherein one face of the cathode is exposed to the air while a second face of the cathode is exposed to the wastewater, wherein the interphase provides a passage for oxygen diffusion. In addition, the electrode spacing in these systems restricts scaling the chambers to commercial sizes or capacities.